Wind hydrogen energy system and the gradual replacement of natural gas in the State of Ceará – Brazil

The original model for the solar hydrogen energy system created by Veziroglu and Basar in the 70’s was adapted to the State of Ceará – Brazil. The State of Ceará has one of the greatest wind potentials in Brazil and it is estimated to be around 35 GW. At the present year, there are 494 MW wind farms in operation. The aforementioned State also has a natural gas grid of pipelines serving a great number of consumers. There are studies in literature considering the injection of hydrogen into the natural gas pipeline up to 20% in volume without substantial modifications in the natural gas infrastructure. The main objective of this article is to use that model in order to evaluate long term scenarios in which the off peak wind generated hydrogen gradually replaces natural gas in such important State of Brazil. The system is supposed to start in the year 2015 and the economical revenue when it is fully implemented can reach respectively US$ 730 million or US$ 1 billion in the slow or fast scenario of hydrogen introduction into the energy matrix of that important State of Brazil.     

Effect of hydrogen addition on the route preference in natural gas flow in regular,horizontal T-junctions

During the transport of natural gas through pipelines small amounts of condensate can be formed due to temperature and pressure changes. If this natural gas/condensate flow arrives at a regular, sharp-edged T-junction in the pipeline system an interesting phenomenon may be observed i.e. unequal phase splitting of gas and condensate. In this paper its has been shown that the addition of hydrogen into a natural gas stream results in a different splitting behaviour in comparison with the natural gas flow without hydrogen addition.     

我国天然气消费利用现状和发展趋势

分析了我国的天然气消费利用现状：天然气消费量增长迅速,在全国一次能源中的消费比例仍较低（2％～3％）;开始大规模利用境外管道气;国家天然气基干管网框架基本形成,天然气供应格局呈现“西气东输、海气上岸、北气南下”及“就近外供”的局面;天然气市场已基本覆盖全国,西南地区是天然气主要消费市场;消费结构逐渐由以化工为主的单一结构向城市燃气、工业燃料为主的多元结构转变;天然气定价机制不完善,天然气价格相对较低。对我国天然气消费利用发展进行了展望：天然气消费量仍将快速增长,2020年全国天然气需求量将超过2500×10^8m^3;天然气消费中心将继续“南下东移”,长三角、东南沿海和环渤海地区是未来的天然气主要消费市场：天然气消费结构不断优化,城市燃气和工业燃料将成为主要利用方向;天然气定价机制逐步理顺,市场对气价的承受能力不断提高。     

Systematic approach to natural gas usage for domestic heating in urban areas

Natural gas can be used for satisfying population needs for heating, either directly by bringing the gas to the dwellings through the gas distribution system and combusting it in the domestic boiler (gas distribution system—G) or indirectly by combusting the natural gas in the heating plant and distributing the heat energy to the dwellings through the district-heating (DH) system. The selection of a certain type of heating system is made according to the disposition of buildings in the area, their number, size, insulation quality, etc. Based on these characteristics, calculations of investments and exploitation costs have been made for both heating systems and a comparison has been made for all of the 96 presented cases. Almost each type of real settlement can be represented by one of the types of the conditional urban area that are introduced in the paper. The main goal of this paper is to establish a general model to achieve coordinated development of centralized energy supply systems fueled by natural gas, based on defined and accepted criteria. A structure analysis of centralized systems for energy supply has been done with accent on their pipelines.     

Can deployment of renewable energy put downward pressure on natural gas prices?

High and volatile natural gas prices have increasingly led to calls for investments in renewable energy. One line of argument is that deployment of these resources may lead to reductions in the demand for and price of natural gas. Many recent US-based modeling studies have demonstrated that this effect could provide significant consumer savings. In this article we evaluate these studies, and benchmark their findings against economic theory, other modeling results, and a limited empirical literature. We find that many uncertainties remain regarding the absolute magnitude of this effect, and that the reduction in natural gas prices may not represent an increase in aggregate economic wealth. Nonetheless, we conclude that many of the studies of the impact of renewable energy on natural gas prices appear to have represented this effect within reason, given current knowledge. These studies specifically suggest that a 1% reduction in US natural gas demand could lead to long-term average wellhead price reductions of 0.8–2%, and that each megawatt-hour of renewable energy may benefit natural gas consumers to the tune of at least $7.5–20.     

The development of a natural gas transportation logistics management system

Efficient management of the natural gas business chain – based on pipeline transmission networks and taking into consideration the interaction among the main players (e.g., shippers, suppliers, transmission companies and local distribution companies) – requires the use of decision-making support systems. These support systems maximise resources and mitigate contingencies due to gas supply shortfalls, operational contingencies from scheduled and non-scheduled equipment outages and market demand shortfalls. This study presents a practical use for technologies, such as a thermohydraulic simulation of gas flow through pipelines, a Monte Carlo simulation for compressor station availability studies, an economic risk evaluation related to potential revenue losses and contractual penalties and linear programming for the maximisation of income and the minimisation of contractual penalties. The proposed system allows the optimum availability level to be defined and maintained by the Transporter (by installing reserve capacity) to mitigate losses related to revenue and contractual penalties. It also economically identifies, quantifies and justifies the installation of stand-by compressor units that can mitigate the Transporter’s exposure to losses caused by capacity shortfalls as a consequence of scheduled and non-scheduled outages.     

Long term forecasting of natural gas production

Natural gas is an important energy source for power generation, a chemical feedstock and residential usage. It is important to analyse the future production of conventional and unconventional natural gas. Analysis of the literature determined conventional URR estimates of 10,700–18,300 EJ, and the unconventional gas URR estimates were determined to be 4250–11,000 EJ. Six scenarios were assumed, with three static where demand and supply do not interact and three dynamic where it does. The projections indicate that world natural gas production will peak between 2025 and 2066 at 140–217 EJ/y (133–206 tcf/y). Natural gas resources are more abundant than some of the literature indicates.     

China’s natural gas reform: why and how

Natural gas is playing an extremely significant role in implementing green and low-carbon economy in China, while its share in energy mix only accounted for 6.4% of China’s total energy consumption in 2016. The Chinese government began to make a series of policies and measures to catalyze natural gas production and consumption for dealing with severe air pollution and optimizing energy structure. Some key issues such as highly regulated natural gas pricing system, the monopoly of natural gas pipelines, and the dominance of state-owned oil companies are substantially existing to be addressed in the forthcoming natural gas reforms. The dilemma of reforms is analyzed in this article and the related reform solutions are to be explored in the deregulation of Chinese natural gas pricing mechanism, separation of state-owned companies’ pipeline, and nondiscriminatory third-party access. The results show that Chinese natural gas reform is destined to be a long-lasting war.     

Flow characteristics of hydrogen gas through a critical nozzle

Critical nozzles are widely used in the flow measurement and can be used for mass flow-rate measurement of hydrogen gas. The effect of real gas state equation on discharge coefficient of hydrogen gas flow through a critical nozzle was investigated. The real gas critical flow factor was introduced which considers the effect of the real gas on discharge coefficient. An analytic solution of real gas critical flow factor of hydrogen gas calculated from the modern equations of state based on Helmholtz energy, over a wider range of temperature 150–600 K and pressure up to 100 MPa was presented. An accurate empirical equation for real gas critical flow factor was determined by the nonlinear regression analysis. The equation was in good agreement with the high-pressure hydrogen gas experimental data by Morioka and CFD solutions by Nagao and Kim. Using this equation, the discharge coefficient can be directly and accurately calculated. It indicates that the discharge coefficient of hydrogen gas should be comprehensively taken into consideration with stagnation temperature, stagnation pressure and nozzle throat diameter. A lot of detailed results about the effect of real gas state equation were obtained.     

A multi-criteria approach to evaluate the natural gas energy systems

This paper aims to select the optimal energetic scenario applied to a consumer with 100 000 inhabitants from the residential–tertiary sector, from the ecological, energetical and economic points of view. A series of seven scenarios based on natural gas has been analyzed. The authors proposed six scenarios for the combined heat and power generation using existing technologies and one scenario for separate generation of the two energy forms. To compare the seven energetic scenarios, the amount of thermal and electrical energy produced by each one had to be the same for a defined time period. To select the optimal energy scenario a multi-criteria NAIADE-based method has been used. Consequently, the optimal energy scenario has been established with respect to criteria groups: ecologic, economic, energetic and global where all criteria groups have been considered. The study results prove that a combined gas and steam turbine cycle is optimal technically, economically and ecologically as it is for each criteria group. A sensitivity analysis has been performed to establish the influence of various parameters in the identification of the optimal energy scenario. For all analyzed scenarios, the optimal energetic scenario is the combined gas and steam turbine cycle.     

俄罗斯与天然气出口过境国的争端和启示

俄罗斯是世界上最重要的天然气生产和出口国之一,其天然气探明储量为44.8×1012m3,约占全球总量的23.9%。然而由于缺少直通消费国的输气管道,绝大部分天然气出口必须过境第三国。近年来,俄罗斯与乌克兰、白俄罗斯、土耳其、波兰等主要出口过境国在过境费、天然气价格、债务和贷款等问题上冲突不断,影响了俄罗斯对主要天然气消费市场的供应,成为制约俄罗斯天然气工业发展的不利因素。为了消除天然气出口的"瓶颈",俄罗斯开始加强与消费国的联系,提出绕过第三方的输气管道方案;而过境国也使出浑身解数,希望利用自己在俄罗斯天然气出口中的作用获得更多利益。我国已成为名副其实的能源进口大国,因此俄罗斯与其天然气出口过境国和欧洲间的博弈,对我国的能源安全有重要的借鉴意义。从长期来看,天然气很可能在世界一次能源消费从化石燃料向非化石燃料的过渡中发挥重要作用,我国应从国家和石油公司两个层面重视天然气生产,优化能源结构;应加快实现我国油气进口来源地和运输途径的多元化;能源进口单位应提高公关意识,特别是危机公关,处理好与供应国和过境国之间的关系;同时应增加天然气储备,建立国家层面的战略储备和企业层面的调峰储备。     

Advancing in the decarbonized future of natural gas transmission networks through a CFD study

The injection of green hydrogen into the natural gas grid is a way to decarbonize the gas sector and build an economic transport route for the large-scale delivery of hydrogen. The suitability of the natural gas infrastructure for this purpose depends on the impact that hydrogen may have on the correct operation of its components and understanding the new flow conditions in the system is essential for this aim. Computational studies can anticipate the expected environment in the pipe system, assessing the readiness of the system. However, the experience on this topic is not extensive enough and deeper understanding is necessary. Here we show a CFD study to simulate the transport of H₂/NG blends in a gas setup with the main characteristics of injection sites and gas pipelines representatives of the transmission gas network. This setup considers a blending station, the pumping and injection procedure, and different pipelines geometries to predict the behavior of various mixtures of H₂/NG. It can be seen how (1) a good mixing is achieved in the blending station after a pipe length equivalent to 20–30 diameters is reached; (2) pumping gas by a piston type compressor shows pulsations in the flow regardless the composition of the blend that can be damped implementing mitigation measurements; and (3) asymmetries in the flow are found when the direction of the fluid changes after section reduction, but 20 diameters downstream of the reduction the flow is fully developed.     

Hydrogen effects on X80 pipeline steel in high-pressure natural gas/hydrogen mixtures

Blending hydrogen into existing natural gas pipelines has been proposed as a means of increasing the output of renewable energy systems such as large wind farms. X80 pipeline steel is commonly used for transporting natural gas and such steel is subjected to concurrent hydrogen invasion with mechanical loading while being exposed to hydrogen containing environments directly, resulting in hydrogen embrittlement (HE). In accordance with American Society for Testing and Materials (ASTM) standards, the mechanical properties of X80 pipeline steel have been tested in natural gas/hydrogen mixtures with 0, 5.0, 10.0, 20.0 and 50.0vol% hydrogen at the pressure of 12 MPa. Results indicate that X80 pipeline steel is susceptible to hydrogen-induced embrittlement in natural gas/hydrogen mixtures and the HE susceptibility increases with the hydrogen partial pressure. Additionally, the HE susceptibility depends on the textured microstructure caused by hot rolling, especially for the notch specimen. The design calculation by the measured fatigue data reveals that the fatigue life of the X80 steel pipeline is dramatically degraded by the added hydrogen.     

Natural gas contracts in an emerging competitive market

The price and duration of natural gas contracts are analysed to determine that electric and gas utilities in the USA can obtain long-run reliable supplies of natural gas at prevailing market prices. Open access to gas transmission lines has created a market with a large number of buyers and sellers that provides reliable gas supplies. The transaction cost literature on contracts suggests that spot purchases and short-term contracts have become more efficient than the long-term fixed price contracts that typifield the gas industry before the 1980s. An efficient supply of gas requires increasing contracting options and reducing regulatory approval of contracts. For instance, gas marketers, with access to local distribution of pipelines, could offer customers a menu of contract choices for gas and energy services. Alternatively, distribution companies could offer their customers a diversity of contracts. Some regulatory inefficiencies are avoided by automatically setting the allowable cost of gas to current market prices.     

基于改进两部制的天然气管输定价研究

近年来我国部分城市相继出现天然气供应紧张局面,天然气短缺暴露了现行天然气定价机制的不足.研究科学合理的天然气管输定价方法,对于完善我国天然气定价机制,确定合理的天然气价格具有十分重要的作用.目前,我国主要采取“老线老价、新线新价”的天然气管输定价方法.对于“老线老价”,天然气管输定价参照铁路运输定价方法具有很大的不科学性.“新线新价”虽然在很大程度上解决了过去管道运输定价机制套用铁路运价所带来的问题,但也存在许多不足,如无法真实反映价值、没有考虑到天然气工业的发展阶段、无法反映用户结构的多样性、没有反映出供求关系以及无法起到削峰填谷的作用等.目前我国受管制行业广泛采用两部制定价方法,这虽然有利于实现经济福利最大化,但它是以固定费用的征收不会使消费者退出消费市场为前提的,没有考虑不同消费者的价格承受能力,也没有考虑需求量的波动,因此在原有两部制的基础上做出改进,使其更加科学合理.     

Modeling and forecasting natural gas demand in Bangladesh

Natural gas is the major indigenous source of energy in Bangladesh and accounts for almost one-half of all primary energy used in the country. Per capita and total energy use in Bangladesh is still very small, and it is important to understand how energy, and natural gas demand will evolve in the future. We develop a dynamic econometric model to understand the natural gas demand in Bangladesh, both in the national level, and also for a few sub-sectors. Our demand model shows large long run income elasticity – around 1.5 – for aggregate demand for natural gas. Forecasts into the future also show a larger demand in the future than predicted by various national and multilateral organizations. Even then, it is possible that our forecasts could still be at the lower end of the future energy demand. Price response was statistically not different from zero, indicating that prices are possibly too low and that there is a large suppressed demand for natural gas in the country.     

Fire prevention technical rule for gaseous hydrogen transport in pipelines

This paper presents the current results of the theoretical and experimental activity carried out by the Italian Working Group on the hydrogen fire prevention safety issues in the field of the hydrogen transport in pipelines [Grasso N, Ciannelli N, Pilo F, Carcassi M, Ceccherini F. Fire prevention technical rule for gaseous hydrogen refuelling stations. Proceedings of the International Conference on Hydrogen Safety, 8–10 September 2005, Pisa, Paper 420064]. From the theoretical point of view a draft document has been produced beginning from the Italian regulations in force on the natural gas pipelines; these have been reviewed, corrected and integrated with instructions suitable to use with hydrogen gas. From the experimental point of view a suitable apparatus has been designed and installed at the University of Pisa; this apparatus will allow simulations of hydrogen releases from a pipeline with or without ignition of the hydrogen–air mixture. The experimental data will help the completion of the above-mentioned draft document with the instructions about the safety distances. However, in the opinion of the Group, the work on the text contents is concluded and the document is ready to be discussed with the Italian stakeholders involved in the hydrogen applications.     

Study of cyclic variations of direct-injection combustion fueled with natural gas–hydrogen blends using a constant volume vessel

Cyclic variations of direct-injection combustion fueled with natural gas–hydrogen fuel blends were experimentally studied using a constant volume vessel. Direct-injection combustion was realized by injecting the high-pressure fuel into the vessel. Flame propagating photographs and pressure history in the vessel were recorded at various hydrogen volumetric fractions in the fuel blends (from 0% to 40%) under the same lean-burn conditions where the overall equivalence ratios are 0.6 and 0.8, respectively. The effect of fuel–air mixture inhomogeneous distribution and hydrogen addition on the cyclic variations was analyzed via flame development photographs and pressure-derived combustion parameters. The results indicated that the cyclic variations were initiated at the early stage of flame development. The flame kernel is closely concentric to the spark electrode and flame pattern has less irregular with hydrogen addition. Direct-injection natural gas combustion can achieve the stable lean combustion along with low cyclic variations due to the mixture stratification in the vessel. The cyclic variations decreased with the increase of hydrogen addition and this trend is more obvious at ultra-lean-burn condition. Hydrogen addition weakened the effect from turbulent flow on flame propagating process, thus reduce the cyclic variations related to the gas flow. There exists interdependency between the early combustion stage and the subsequent combustion process for direct-injection combustion.     

Recommendations on X80 steel for the design of hydrogen gas transmission pipelines

By limiting the pipes thickness necessary to sustain high pressure, high-strength steels could prove economically relevant for transmitting large gas quantities in pipelines on long distance. Up to now, the existing hydrogen pipelines have used lower-strength steels to avoid any hydrogen embrittlement. The CATHY-GDF project, funded by the French National Agency for Research, explored the ability of an industrial X80 grade for the transmission of pressurized hydrogen gas in large diameter pipelines. This project has developed experimental facilities to test the material under hydrogen gas pressure. Indeed, tensile, toughness, crack propagation and disc rupture tests have been performed. From these results, the effect of hydrogen pressure on the size of some critical defects has been analyzed allowing proposing some recommendations on the design of X80 pipe for hydrogen transport. Cost of Hydrogen transport could be several times higher than natural gas one for a given energy amount. Moreover, building hydrogen pipeline using high grade steels could induce a 10 to 40% cost benefit instead of using low grade steels, despite their lower hydrogen susceptibility.